Define Prototype Method

Safely defines methods on JavaScript prototypes (including built-ins) in an idempotent and non-enumerable manner.

definePrototypeMethod

Safely defines methods on JavaScript prototypes (including built-in prototypes like String.prototype, Array.prototype, etc.) in an idempotent manner. The defined method is non-enumerable by default and will not overwrite existing methods unless explicitly configured to do so.

Function Signature

function definePrototypeMethod<Proto extends object, Name extends keyof Proto>(
  proto: Proto,
  name: Name, 
  impl: (...args: unknown[]) => unknown,
  options?: ProtoMethodOptions
): void

Parameters

Parameter	Type	Description
`proto`	`Proto`	The target prototype object (e.g. `String.prototype`).
`name`	`Name`	The method name to define on the prototype.
`impl`	`Function`	The function implementation of the method.
`options`	`ProtoMethodOptions` (optional)	Property descriptor settings and overwrite options.

Example Usage

playground.ts

Behavior Details

Non-Enumerable by Default

By default, the defined method is marked non-enumerable (enumerable: false). This guarantees that it behaves exactly like native prototype methods and won't leak or appear during property iterations like for...in loops or Object.keys().

Types

`ProtoMethodOptions`

interface ProtoMethodOptions {
  overwrite?: boolean;     // Defaults to false. If true, overrides existing properties.
  enumerable?: boolean;    // Defaults to false. If true, makes property enumerable.
  configurable?: boolean;  // Defaults to false.
  writable?: boolean;      // Defaults to true.
}

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